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Luring mosquitoes into honey-laden traps could make tracking deadly diseases much easier, say scientists.

Australian researchers writing in the Proceedings of the National Academy of Sciences today (7 June) report on a simple method to obtain viruses from mosquitoes' saliva left behind when they feed on sugar.

Surveillance of viruses spread mainly by blood-sucking insects (arboviruses) — such as dengue, West Nile and chikungunya — is vital for making public health decisions about outbreaks. But detecting the viruses in their human or animal reservoirs and mosquito carriers is laborious, time-consuming and expensive. 

The researchers put honey-soaked filter paper cards in traps. The RNA — a form of genetic material related to DNA — was extracted and identified using a process called RT-PCR, which transcribes the RNA into its DNA equivalent and amplifies it.

The method was comparable with laborious mosquito-processing methods and better than conventional techniques at picking up arboviruses in wild mosquito populations.

Andrew van den Hurk, a researcher in the Department of Virology at the Queensland Health Forensic and Scientific Services, and co-author of the paper, told SciDev.Net the technique could be used for any virus and that it could be easier and cheaper for virus surveillance in developing countries, most of which have PCR facilities.

"Instead of processing thousands of mosquitoes and running hundreds of PCR tests, you could process just 4-6 of these cards."

And because the cards deactivate the virus, rendering it non-infectious, countries without PCR facilities could courier the cards to other countries for analysis.

Less labour means the test is faster, so the system would be a useful early warning system for either newly emerging or re-emerging viruses, said van den Hurk. "Take Rift Valley Fever surveillance in Africa. That's a virus where you don't see much activity but then, after flooding rain, you'll get outbreaks. It could be used for early warning detection."

Duane Gubler, director of the Asian Pacific Institute of Tropical Medicine and Infectious Diseases, said that the method "could be a great asset to enhance surveillance" of diseases that have animal hosts and are often detected by testing 'sentinel animals' for infection.

"The only question is how many PCR tests would have to be done. For human diseases, I still think it is more cost effective to monitor the human population" he said.

Link to full article in Proceedings of the National Academy of Sciences

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